Systems and methods for optical anesthetic agent level sensors

Abstract

The present invention provides a system and method for anesthetic agent level sensing. In one embodiment, a system for a level sensor for an anesthetic agent vaporizer includes: a measuring tube (302) including a float (304) positioned therein, a bottom portion of the measuring tube being coupled to a cover (306) having a central opening; a retaining bracket coupled to a top portion of the measuring tube; an optical sensor (318) housed in the retaining bracket, including a light source positioned to emit light toward the interior of the measuring tube and a light detector positioned to receive light from the interior of the measuring tube; and an optical window housed in the retaining bracket and coupled between the optical sensor and the interior of the measuring tube.

Description

Technical Field

[0001] Embodiments of the subject matter disclosed herein relate to anesthesia systems, and more particularly, to systems and methods for monitoring the level of anesthetic agent remaining in an anesthetic agent vaporizer. Background Art

[0002] During some medical procedures, such as surgical procedures, a patient may be placed under general anesthesia by administering an anesthetic. In some examples, the anesthetic may be a volatile anesthetic that is administered to the patient via an anesthetic vaporizer. For example, the anesthetic vaporizer may cause and control the vaporization of a volatile anesthetic from a liquid form. A carrier gas (e.g., a mixture of oxygen and fresh air) may flow into the vaporizer and blend (e.g., mix and converge) with the anesthetic vapor before flowing to the patient, where the gases may be introduced, for example, via inhalation.

[0003] Conventional anesthetic vaporizers include a reservoir for storing liquid anesthetic before it is vaporized and delivered to a patient for inhalation. An operator (e.g., an anesthesiologist or other clinician) can monitor the level of liquid anesthetic in the reservoir before and during use to ensure that sufficient anesthetic is available for delivery to the patient during a medical procedure. Summary of the invention

[0004] In one embodiment, a system for a level sensor for an anesthetic agent vaporizer includes: a measuring tube including a float positioned therein, a bottom portion of the measuring tube coupled to a cover having a central opening; a retaining bracket coupled to a top portion of the measuring tube; an optical sensor housed within the retaining bracket, including a light source positioned to emit light toward an interior of the measuring tube and a light detector positioned to receive light from the interior of the measuring tube; and an optical window housed within the retaining bracket and coupled between the optical sensor and the interior of the measuring tube. In this manner, the level sensor is capable of providing anesthetic agent level measurements with increased accuracy.

[0005] It should be understood that the above brief description is provided to introduce in a simplified form selected concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is solely defined by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present disclosure will be better understood by reading the following description of non-limiting embodiments with reference to the accompanying drawings, in which:

[0007] Figure 1An exemplary embodiment of an anesthesia machine is schematically shown.

[0008] Figure 2 An exemplary embodiment of an anesthetic agent vaporizer that may be included in an anesthesia machine is schematically illustrated.

[0009] Figure 3 A top perspective cross-sectional view of an exemplary embodiment of an optical level sensor that may be coupled in a sump of an anesthetic agent vaporizer is shown.

[0010] Figure 4 An exemplary embodiment of a time-of-flight proximity sensor that may be included in an optical level sensor for determining anesthetic volume is shown.

[0011] Figure 5 A diagram showing light emission and light detection by a time-of-flight proximity sensor included in an optical level sensor for determining anesthetic volume is shown.

[0012] Figure 6 Example graphs illustrating continuous measurements of distance to the surface of liquid anesthetic agent by a time-of-flight proximity sensor included in an optical level sensor are described.

[0013] Figure 7 An example graph showing the relationship between the measured distance to the surface of the liquid anesthetic agent in the reservoir and the volume of the liquid anesthetic agent in the reservoir.

[0014] Figure 8 An example timeline for determining the volume of liquid anesthetic agent in a reservoir via an optical level sensor is schematically illustrated.

[0015] Fig. 9 is a flow chart illustrating an exemplary embodiment of a method for determining an emptying time of an anesthetic agent vaporizer tank based on measurements made by an optical level sensor. DETAILED DESCRIPTION

[0016] The following description relates to various embodiments for measuring and monitoring the liquid level of a liquid anesthetic in an anesthetic vaporizer, which may be included in an anesthesia machine. Currently available anesthetic level sensors (such as capacitive, acoustic / ultrasonic, and differential static pressure level sensors) may be affected by the characteristics of the liquid anesthetic. For example, the liquid anesthetic is a halogenated solvent that can react violently with certain materials and / or deposit residues over time, such as a film composed of butylated hydroxytoluene (BHT). As an example, changes in the dielectric properties of the liquid anesthetic caused by BHT deposition over time may affect the measurement performed by the capacitive level sensor. As another example, an acoustic / ultrasonic level sensor may be affected by changes in humidity and the temperature of the liquid anesthetic. As yet another example, a differential static pressure level sensor may be incompatible with reactive anesthetics. As a result, the sensor mentioned above may not accurately measure the anesthetic level, and therefore cannot accurately measure the anesthetic volume across time and conditions.

[0017] Therefore, according to the embodiments disclosed herein, a liquid level sensor that is not affected by changes in the characteristics of liquid anesthetics is provided. In the embodiments disclosed herein, the liquid level sensor is connected in a storage tank storing liquid anesthetics, and includes a measuring tube and a float positioned therein. According to the embodiments disclosed herein, the float moves vertically in the measuring tube and is located at the surface of the liquid anesthetic. In the embodiments disclosed herein, the liquid level sensor includes an optical sensor, which includes a light source positioned to emit light toward the float in the measuring tube and a light detector positioned to receive light reflected by the float. In addition, the optical sensor can be coupled to an electronic controller, which can receive a signal output corresponding to the distance between the float and the optical sensor from the optical sensor, and the controller can use the signal output to determine the volume of the liquid anesthetic remaining in the storage tank and the emptying time. In some embodiments, the controller can output a refill alarm in response to the emptying time being shortened to below a threshold duration.

[0018] Embodiments disclosed herein can provide several advantages. For example, the optical sensor can measure a physical distance between a float and the sensor that is insensitive to the physical characteristics of the liquid anesthetic, thereby increasing the accuracy of the measurement performed by the optical sensor. In addition, the physical distance is reproducibly related to a calculable volume of the liquid anesthetic, thereby achieving a more accurate volume calculation. As another example, embodiments disclosed herein provide a liquid level sensor with a small form factor that is reagent compatible. In addition, for example, by determining the drain time and outputting a refill alarm, it can be ensured that there is enough anesthetic available for delivery to the patient during the medical procedure, without the operator of the anesthetic vaporizer having to closely monitor the liquid level, thereby freeing the operator from concerns about patient monitoring.

[0019] Figure 1 An exemplary embodiment of an anesthesia machine is schematically shown. Figure 2 shows what can be included in Figure 1 An exemplary embodiment of an anesthetic agent vaporizer in an anesthesia machine. Figure 3 Shows that it can be connected to Figure 2 A cross-sectional view of an exemplary embodiment of a liquid level sensor in a tank of an anesthetic agent vaporizer. The liquid level sensor may include at least one light source and at least one light detector, such as Figure 4 As shown, the distance from the level sensor to the float on the surface of the liquid anesthetic agent can be measured based on the light reflection of the float, as shown in FIG. Figure 5 shown. Figure 6 depicts an example graph of how the measured distance may change over time as the tank is emptied, and Figure 7 An example graph showing the relationship between measured distance and volume of liquid anesthetic agent in a reservoir is shown. Figure 8 An example timeline is shown showing how the level of the float and the corresponding distance measured by the level sensor changes as the level (and volume) of the liquid anesthetic agent in the reservoir changes. The controller can track the volume of the liquid anesthetic agent in the reservoir during use and warn the operator to refill the reservoir when the remaining operating time is low, such as based on Fig. 9 Likewise, depending on the current fresh gas flow rate and output anesthetic agent concentration, the controller can calculate and display the instantaneous "empty time".

[0020] Figure 1An example anesthesia machine 100 is schematically shown. Anesthesia machine 100 includes a frame (or housing) 102. In some embodiments, frame 102 can be supported by casters, wherein the movement of the casters can be controlled (e.g., stopped) by one or more locks. In some examples, frame 102 can be formed of a plastic material (e.g., polypropylene). In other examples, frame 102 can be formed of a different type of material (e.g., a metal such as steel).

[0021] The anesthesia machine 100 also includes an anesthesia display device 104, a patient monitoring display device 106, a breathing gas module 108, one or more patient monitoring modules (such as a patient monitoring module 110), a ventilator 112 (explained in more detail below), an anesthetic agent vaporizer 114, and an anesthetic agent reservoir 116. The anesthesia machine 100 may also include a main power indicator 124, a system activation switch 126 (in one example, the system activation switch allows gas flow when activated), an oxygen flush button 128, and an oxygen control 130. Example embodiments of the anesthetic agent vaporizer 114 will be described below with respect to Figure 2 The anesthetic agent vaporizer 114 may vaporize the anesthetic agent and combine the vaporized anesthetic agent with one or more medical grade gases (eg, oxygen, air, nitrous oxide, or a combination thereof), which may then be delivered to a patient.

[0022] The anesthesia machine 100 may further include an integrated suction device, an auxiliary oxygen flow controller, and various other components for providing and / or controlling the flow of one or more medical-grade gases to the patient. For example, the anesthesia machine 100 includes one or more pipe connectors 146 to facilitate coupling the anesthesia machine to a pipeline gas source. In addition, the anesthesia machine 100 includes a cylinder bracket 144, and one or more gas holding cylinders 148 can be coupled to the anesthesia machine via the cylinder bracket. Therefore, gas can be provided to the anesthesia machine through a pipe connection and / or a cylinder connection, wherein the gas may include but is not limited to air, oxygen, nitrogen, and nitrous oxide. As described above, the gas entering the anesthesia machine can be mixed with the gasified anesthetic at the anesthetic gasifier 114, and then supplied to the patient via the respirator 112. The anesthesia machine may also include a serial port, a collection bottle connector, a cylinder wrench storage area, and an anesthetic gas removal system.

[0023] The ventilator 112 may include an exhalation check valve at an exhalation port 120, an exhalation flow sensor at the exhalation port 120, an inhalation check valve at an inhalation port 118, an inhalation flow sensor at the inhalation port 118, an absorbent tank, a manual airbag port, a ventilator release device, an adjustable pressure limiting valve, an airbag / exhaust switch, and a bellows assembly. When the patient breathing circuit is connected to the ventilator 112, breathing gas (e.g., air, oxygen, and / or nitrous oxide mixed with vaporized anesthetic) leaves the anesthesia machine from the inhalation port 118 and travels to the patient. The exhalation gas from the patient reenters the anesthesia machine via the exhalation port 120, where carbon dioxide can be removed from the exhalation gas via the absorbent tank.

[0024] During operation of the anesthetic gasifier 114, an operator (e.g., an anesthesiologist) can adjust the amount of vaporized anesthetic supplied to the patient by adjusting the flow of gas from a gas source (e.g., a pipeline gas supply) to the gasifier. The operator can adjust the gas flow from the gas source to the gasifier by adjusting one or more flow regulating devices. For example, the flow regulating device may include an analog and / or digital adjustment dial and / or other user input device configured to actuate one or more flow control valves of the anesthesia machine 100. In some embodiments, a first flow control valve may be positioned between the gas source and the anesthetic gasifier 114, and may be capable of being actuated to a fully open position, a fully closed position, and a plurality of positions between the fully open position and the fully closed position via the flow regulating device.

[0025] The anesthesia machine 100 may further include one or more valves configured to allow gas from the gas source to bypass the anesthetic agent vaporizer 114. The valves may allow a first portion of gas to flow directly from the gas source to the inspiratory port 118, and allow a second portion of gas to flow from the gas source through the anesthetic agent vaporizer 114 to mix with the vaporized anesthetic agent before flowing to the inspiratory port 118. By adjusting the ratio of the first portion of gas to the second portion of gas, the operator can control the concentration of the vaporized anesthetic agent administered to the patient via the inspiratory port 118.

[0026] In addition, the above-mentioned regulation can be facilitated based at least in part on the output from the breathing gas module 108. The breathing gas module 108 can be configured to measure various parameters of the gas leaving the gasifier and / or being provided to the patient. For example, the breathing gas module 108 can measure the concentration of carbon dioxide, nitrous oxide, and anesthetic provided to the patient. In addition, the breathing gas module 108 can measure the respiratory rate, minimum alveolar concentration, patient oxygen, and / or other parameters. The output of the breathing gas module 108 can be displayed on a display device (e.g., anesthesia display device 104 and / or patient monitoring display device 106) via a graphical user interface and / or used by the controller to provide closed-loop feedback control of the amount of anesthesia provided to the patient.

[0027] The ventilator 112 may optionally be coupled to a breathing circuit (not shown) comprising a plurality of tubes (e.g., gas channels) 122. The breathing circuit may be coupled between the patient's airway (e.g., via a breathing mask positioned to surround the patient's mouth and / or nose or an endotracheal tube) and an inspiratory port 118. A gas (e.g., one or more medical gases or a mixture of one or more medical gases and a vaporized anesthetic from an anesthetic vaporizer 114) may flow from the inspiratory port 118 through the breathing circuit and into the patient's airway, where the gas is absorbed by the patient's lungs. By adjusting the concentration of the vaporized anesthetic in the gas as described above, the operator may adjust the degree of anesthesia of the patient.

[0028] During a state in which the breathing circuit is coupled to the airway, an anesthetic agent and / or fresh gas (without an anesthetic agent) may flow into the patient's airway (e.g., by inhalation) via the inspiratory port 118 and the inspiratory check valve. For example, the inspiratory check valve may automatically open in response to the patient's inhalation (e.g., without operator input or adjustment), and may automatically close in response to the patient's exhalation. Similarly, the exhalation check valve may automatically open in response to the patient's exhalation, and may automatically close in response to the patient's inhalation.

[0029] In some embodiments, the operator may additionally or alternatively control one or more operating parameters of the anesthesia machine 100 via the electronic controller 140 of the anesthesia machine 100. The controller 140 includes a processor operably connected to a memory. The memory may be a non-transitory computer-readable medium, and may be configured to store computer executable code (e.g., instructions) to be processed by the processor to execute one or more routines (such as those described herein). The memory may also be configured to store data received by the processor. The controller 140 may be communicatively connected (e.g., via a wired or wireless connection) to one or more external or remote computing devices such as a hospital computing system, and may be configured to send and receive various information such as electronic medical record information, procedure information, etc. The controller 140 may also be electrically coupled to various other components of the anesthesia machine 100, such as an anesthetic gasifier 114, a ventilator 112, a respiratory gas module 108, an anesthesia display device 104, and a patient monitoring display device 106.

[0030] The controller 140 receives signals from various sensors of the anesthesia machine 100 and employs various actuators of the anesthesia machine 100 to adjust the operation of the anesthesia machine 100 based on the received signals and instructions stored on the memory of the controller. For example, the flow of gas to the inspiratory port 118 may be controlled via an input device (e.g., a keyboard, a touch screen, etc.) coupled to an electronic controller of the anesthesia machine 100. The controller 140 may display operating parameters of the anesthesia machine 100 via the anesthesia display device 104 and / or the patient monitoring display device 106. The controller may receive signals (e.g., electrical signals) via the input device and may adjust operating parameters of the anesthesia machine 100 in response to (e.g., in response to) the received signals.

[0031] For example, an operator may input a desired concentration of an anesthetic to be delivered to a patient. The corresponding valve position of one or more valves of the anesthesia machine (e.g., the position of one or more bypass valves, as described above) may be determined empirically and stored in a predetermined lookup table or function in a memory of the controller. For example, the controller may receive a desired anesthetic concentration via an input device, and may determine the opening amount of one or more valves corresponding to the desired anesthetic concentration based on a lookup table, wherein the input is the concentration of the anesthetic and the output is the valve position of one or more valves. The controller may transmit an electrical signal to an actuator of one or more valves so as to adjust each of the one or more valves to a corresponding output valve position. In some examples, for example, the controller may compare a desired gas flow rate with a measured gas flow rate, such as by an inspiratory flow sensor.

[0032] Although the controller 140 Figure 1 1 is shown for illustrative purposes, but it should be understood that the controller 140 can be located at various locations within, around, and / or remote from the anesthesia machine 100. For example, the controller 140 may include a plurality of devices / modules that may be distributed throughout the anesthesia machine 100. Therefore, the controller 140 may include a plurality of controllers at various locations within the anesthesia machine 100. As another example, additionally or alternatively, the controller 140 may include one or more devices / modules located outside the anesthesia machine 100, located near the anesthesia machine 100 (e.g., in the same room), or remote from the anesthesia machine (e.g., a remote server). In each example, the plurality of devices / modules may be communicatively coupled via wired and / or wireless connections.

[0033] Anesthetic agent vaporizers (such as Figure 1The anesthetic agent vaporizer 114 shown in the figure can use various methods to vaporize the liquid anesthetic agent. For example, the anesthetic agent vaporizer can use an overflow method (wherein the carrier gas flows above the top surface of the volatile liquid anesthetic agent), a bubbling method (wherein the carrier gas bubbles upward through the liquid anesthetic agent), or a gas / vapor blender (wherein heat is used to vaporize the liquid anesthetic agent and the vapor is injected into the fresh gas flow). Regardless of the vaporization method, in some embodiments, the anesthetic agent vaporizer 114 can include a storage tank for storing the liquid anesthetic agent before it is delivered to the vaporization chamber.

[0034] Figure 2 A method that may be included in an anesthesia machine (e.g., Figure 1 1. An exemplary embodiment of an anesthetic agent vaporizer 200 in an anesthesia machine 100 shown in FIG. 1. As an example, the anesthetic agent vaporizer 200 may be Figure 1 The anesthetic agent vaporizer 114. Figure 2 In the illustrated embodiment, the anesthetic agent vaporizer 200 is a bubbler-type anesthetic agent vaporizer that includes a vaporization chamber 202 defined by a housing 204. However, in other embodiments, the anesthetic agent vaporizer 200 may be another type of anesthetic agent vaporizer (e.g., aspiration-type, syringe-based, wick-based, etc.) for use with volatile liquid anesthetic agents that includes a controller and liquid level sensing technology.

[0035] The lower portion of the vaporization chamber 202 is shown as holding a liquid anesthetic 210, which is supplied from a reservoir 222 via a conduit 214 and a pump 220. For example, the liquid anesthetic 210 can be isoflurane, sevoflurane, or another liquid anesthetic having similar volatility stored in the reservoir 222. The pump 220 can be a positive displacement pump, such as a reciprocating positive displacement pump. The pump 220 can be selectively operated in response to a command signal from a controller 225 to deliver the liquid anesthetic 210 from the reservoir 222 to the vaporization chamber 202, as will be further described below. The controller 225 can be an electronic controller including a processor operably connected to a memory 228. For example, the controller 225 can be included in Figure 1 The controller 140 (eg, a portion thereof) is shown as being in or communicatively coupled to the controller (eg, a portion thereof).

[0036] The storage tank 222 can be refilled via a filling cap 223 and a filling port (e.g., neck) 227 having an inlet filling port valve 229 positioned therein. The filling cap 223, the filling port 227, and the inlet filling port valve 229 can be included together in a filling assembly. For example, an operator of the anesthetic gasifier 200 can remove the filling cap 223 to refill the storage tank 222 with additional liquid anesthetic 210 (e.g., from a refill bottle) via the filling port 227 and the inlet filling port valve 229, and then put the filling cap 223 back in place to seal the storage tank 222. For example, the filling cap 223 can be a screw cap. In some embodiments, the inlet filling port valve 229 can be a mechanically actuated spring-loaded valve that opens when the refill bottle is attached to the filling port 227 so that the liquid anesthetic 210 can flow from the refill bottle to the interior of the storage tank 222, and closes when the refill bottle is not attached to the filling port 227. Additionally or alternatively, in some embodiments, the inlet fill port valve 229 can be an electronically actuated valve that can be adjusted in response to a control signal received from the controller 225, as will be further described below. Thus, in some embodiments, the inlet fill port valve 229 can be both mechanically and electronically actuated. Thus, when the fill cap 223 is in place, the sump 222 can be a sealed system.

[0037] The conduit 214 may further include a shutoff valve 218 coupled between the pump 220 and the vaporization chamber 202. For example, the shutoff valve 218 may be a switch valve, wherein the shutoff valve 218 is actuated to an open (e.g., fully open) position that allows the liquid anesthetic agent 210 to flow between the pump 220 and the vaporization chamber 202 or a closed (e.g., fully closed) position that prevents (e.g., blocks) the liquid anesthetic agent 210 from flowing between the pump 220 and the vaporization chamber 202. For example, the shutoff valve 218 may be actuated between the open position and the closed position in response to a command signal from the controller 225. A liquid return line 215 may be coupled to the conduit 214 between the shutoff valve 218 and the pump 220 to reduce pressure buildup between the shutoff valve 218 and the pump 220, such as when the shutoff valve 218 is closed. For example, excess liquid anesthetic agent 210 provided by the pump 220 may be returned to the sump 222 via the liquid return line 215. Additionally, the liquid return line 215 may include a restriction 217 , such as an orifice, to control flow through the liquid return line 215 such that when the shutoff valve 218 is open, the liquid anesthetic agent 210 preferentially flows through the shutoff valve 218 rather than the restriction 217 .

[0038] The controller 225 can selectively activate the pump 220 to provide the liquid anesthetic agent 210 from the reservoir 222 to the vaporization chamber 202. In one embodiment, the controller 225 can adjust the operation of the pump 220 in response to the measurement received from the level sensor 224. For example, the level sensor 224 can be any type of level sensor (such as an optical, ultrasonic, capacitive, float, or pressure-based level sensor) that is positioned to measure the level of the liquid anesthetic agent 210 in the vaporization chamber 202. As an example, the controller 225 can be configured to maintain the level of the liquid anesthetic agent within a target level or target range to prevent the vaporization chamber 202 from being underfilled or overfilled.

[0039] In some embodiments, the pump 220 may include a positive displacement stepper motor, wherein each positive displacement step of the pump is equal to a specified volume of liquid anesthetic agent 210. In this manner, the pump may be used to accurately fill the vaporizer chamber 202 and prevent overfilling by recording the number of pump steps delivered. This method may also be used to record the volume of anesthetic agent delivered to the vaporizer chamber 202, which may be valuable for vaporizer run time / maintenance analysis (service index), liquid leak detection, accurate determination of the amount of liquid anesthetic agent remaining and available for delivery, vaporization efficiency calculations, etc.

[0040] The anesthetic agent vaporizer 200 includes an additional level sensor 230 positioned to measure the level of the liquid anesthetic agent 210 in the reservoir 222. Figure 2 In the illustrated embodiment, the level sensor 230 comprises an optical time-of-flight (ToF) proximity sensor, components of which will be described below with respect to Figure 3 and Figure 4 The level sensor 230 acts as a continuous level sensor that is not affected by changes in operating conditions (e.g., temperature and humidity) or changes in the liquid anesthetic agent 210 itself (e.g., dielectric constant). Figures 5 to 9 As further described, the output from the level sensor 230 can be used to determine the volume (eg, amount) of liquid anesthetic agent 210 remaining in the reservoir 222, as well as the remaining duration until an indication is given to refill the reservoir 222. Figure 2In the exemplary embodiment shown in FIG. 2 , the level sensor 230 can be coupled to the top outer surface of the sump 222 and extend into the interior of the sump 222. For example, the elongated portion of the level sensor 230 can extend through an opening in the housing of the sump 222, while the outer portion of the level sensor 230 can form an airtight seal with the sump 222. For example, this configuration can enable the level sensor 230 to perform top-down measurements through the vapor space above the surface of the liquid anesthetic agent 210. Additionally, in the exemplary embodiment of the anesthetic agent vaporizer 200, the level sensor 230 does not contact the bottom interior surface of the sump 222, but the distance between the bottommost surface of the level sensor 230 and the bottom interior surface of the sump 222 can vary. As will be elaborated herein, the distance between the bottommost surface of the level sensor 230 and the bottom interior surface of the sump 222 results in a volume of liquid anesthetic agent 210 not being measured by the level sensor 230 as an additional reserve to help prevent the sump 222 from being completely drained. Additionally, the controller 225 can track the level (or volume) of the liquid anesthetic agent 210 in the reservoir 222 during refilling via measurements received from the level sensor 230. In embodiments where the inlet fill port valve 229 is electronically actuated, the controller 225 can actuate the inlet fill port valve 229 to close in response to the measured level (or volume) reaching a maximum level (or volume) to prevent the reservoir 222 from inadvertently overfilling / overflowing.

[0041] The upper portion of the vaporization chamber 202 (e.g., above the surface of the liquid anesthetic agent 210) contains a vapor, which may be a mixture of the vaporized anesthetic agent and a carrier gas from a fresh gas stream. The fresh gas stream, and therefore the carrier gas, may contain one or more medical grade gases, such as oxygen, air, nitrous oxide, and combinations thereof. The fresh gas stream may be delivered to the patient via one or more gas conduits (e.g., via a Figure 1 The conduit connector 146 shown) and / or one or more gas holding cylinders (e.g., Figure 1 The gas holding cylinder 148 is provided. Figure 2 As shown, the fresh gas flow may enter the anesthetic agent vaporizer 200 via the first gas passage 236. A first mass flow sensor 241 may be coupled to the first gas passage 236 to measure the flow rate of the fresh gas flow entering the anesthetic agent vaporizer 200. For example, the first mass flow sensor 241 may be an ultrasonic flow meter or a calorimetric (thermal) mass flow meter.

[0042] exist Figure 2In an exemplary embodiment of the invention, the second gas channel 238 branches from the first gas channel 236 downstream of the first mass flow sensor 241 to provide a carrier gas to the vaporizer 202. As used herein, "carrier gas" refers to a portion of the fresh gas flow that flows to the vaporizer 202, while "bypass gas" refers to the remaining portion of the fresh gas flow that does not flow through the vaporizer 202, as will be described in detail below. For example, the second gas channel 238 can pass through an opening in the housing 204, which can include an airtight seal to allow the carrier gas to flow through the bottom of the vaporizer 202. However, in other embodiments, the anesthetic gasifier 200 may not include the second gas channel 238, and the carrier gas may not be delivered to the vaporizer 202. For example, when the liquid anesthetic 210 has a relatively low boiling point (e.g., at or near room temperature), such as when the liquid anesthetic 210 is desflurane or another liquid anesthetic with similar volatility, the carrier gas may not be delivered to the vaporizer 202. Additionally or alternatively, the second gas passage 238 may not be included in embodiments in which a different type of anesthetic agent vaporizer architecture is used (e.g., a flooded type or a gas / vapor blender). Figure 2 The illustrated embodiments are provided by way of example.

[0043] The carrier gas delivered to the vaporization chamber 202 via the second gas passage 238 flows through the liquid anesthetic agent 210 to form a plurality of bubbles 212. The plurality of bubbles 212 pass through the liquid anesthetic agent 210 and become saturated with the vaporized anesthetic agent as they rise to the surface of the liquid. In some examples, a heating element can be coupled to or within the vaporization chamber 202 to increase the temperature of the liquid anesthetic agent 210 and provide energy for vaporization (e.g., latent heat of vaporization).

[0044] Vapor (such as a carrier gas saturated with vaporized anesthetic agent) can flow out of the vaporizer chamber 202 via a third gas channel 240 (e.g., a vapor delivery channel). For example, the third gas channel 240 can pass through an opening at or near the top of the housing 204 and form a junction with the first gas channel 236 to fluidly connect an upper portion of the vaporizer chamber 202 to the first gas channel 236. Upstream of the junction with the third gas channel 240 and downstream of the junction with the second gas channel 238, the first gas channel 236 carries a bypass gas portion of the fresh gas flow. The bypass gas does not pass through the vaporizer chamber 202. The bypass gas (not containing vaporized anesthetic agent) and the vapor from the vaporizer chamber 202 (containing the carrier gas saturated with vaporized anesthetic agent) mix at the junction between the first gas channel 236 and the third gas channel 240 and downstream. The mixed gas can then be delivered to the inspiratory branch of the breathing circuit (e.g., via a portion of the first gas channel 236 relative to the second gas channel 238). Figure 1The first gas passage 236 may be coupled to the second mass flow sensor 244 downstream of the junction with the third gas passage 240 to measure the flow rate of the mixed gas leaving the anesthetic agent vaporizer 200. For example, the second mass flow sensor 244 may be an ultrasonic flow meter or a calorimetric mass flow meter. In terms of the ultrasonic flow metering architecture, the output anesthetic agent concentration may be calculated by the difference in the measured flight time between the upstream ultrasonic flow sensor 241 and the downstream ultrasonic flow sensor 244.

[0045] In some embodiments, an independent concentration sensor 256 can be coupled to the first gas channel 236 downstream of the junction with the third gas channel 240. The concentration sensor 256 can be any suitable sensor configured to measure the concentration of the anesthetic agent in the mixed gas. As an example, the concentration sensor 256 can be an optical sensor that transmits light of a suitable wavelength (e.g., infrared) through the mixed gas and determines the concentration of the anesthetic agent based on the absorption of the light by the mixed gas. In other examples, the concentration sensor can be a carbon dioxide or oxygen sensor that measures the concentration of the anesthetic agent based on the displacement of carbon dioxide or oxygen relative to the supply concentration of carbon dioxide or oxygen in the fresh gas flow. The concentration sensor 256 can output a signal indicating the measured anesthetic concentration (e.g., the concentration of anesthetic vapor) in the mixed gas to the controller 225.

[0046] In addition to receiving signals output by the liquid level sensor 224, the liquid level sensor 230, the concentration sensor 256, the first mass flow sensor 241, and the second mass flow sensor 244, the controller 225 may also receive additional signals, including signals from one or more pressure sensors and temperature sensors coupled at various locations throughout the anesthetic agent vaporizer 200. The controller 225 receives signals from Figure 2 various sensor signals, process input data, and use Figure 2 The various actuators of the controller 225 adjust the operation of the anesthetic agent vaporizer 200 based on the received signals and the instructions stored in the memory of the controller. For example, the controller 225 can receive the measurement value from the liquid level sensor 230 and determine the volume of the liquid anesthetic agent 210 remaining in the tank 222 based on the received measurement value, as will be described below with respect to Fig. 9Described. Additionally, the controller may output an alert to an operator in response to the refill indication via a human machine interface (HMI) 226 that is operatively connected to the controller (e.g., via wired or wireless communication). In addition, data may be input to the controller 225 by an operator of the anesthetic vaporizer 200 via the HMI 226. Thus, the HMI 226 may include both a user input device and an output device. The user input device may include one or more of the following: a mouse, a keyboard, a voice input device, a touch input device for receiving gestures from an operator, a motion input device for detecting non-touch gestures and other actions of an operator, and other input devices comparable thereto, and associated processing elements capable of receiving user input from an operator. The output device may include one or more of the following: a display for providing a visual alert or a text-based message (e.g., Figure 1 anesthesia display device 104 and / or patient monitoring display device 106), and a speaker for providing an audible alarm or message.

[0047] Now turn to Figure 3 , showing Figure 2 2 is a top perspective cross-sectional view of the liquid level sensor 230 introduced in FIG. Specifically, Figure 3The example configuration of the liquid level sensor 230 is shown with the relative positioning of various components. In at least one embodiment, if it is shown as directly contacting or directly connecting each other, such elements can be referred to as directly contacting or directly connecting, respectively. Similarly, in at least one embodiment, the elements shown as being adjacent or adjacent to each other can be adjacent or adjacent to each other, respectively. For example, the components arranged to be coplanarly contacted with each other can be referred to as coplanar contact. For example, in at least one example, the elements positioned to be spaced apart from each other and having only space therebetween without other components can be described and quoted as such. For example, the elements shown as being located above / below each other, located on the opposite sides of each other, or located between the left / right sides of each other can be described and quoted as such relative to each other. In addition, as shown in the figure, in at least one example, the topmost element or point of the element can be referred to as the "top" of the component, and the bottommost element or point of the element can be referred to as the "bottom" of the component. As used herein, top / bottom, upper / lower, above / below can be relative to the vertical axis of the figure, and can be used to describe the positioning of the elements in the figure relative to each other. Thus, in one example, the element shown as being located above other elements is vertically positioned above other elements. For another example, the shape of the element shown in the figure can be referred to as having these shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, etc.). In addition, in at least one example, the elements shown as intersecting each other can be referred to as intersecting elements or intersecting each other. In addition, in one example, the element shown as being located in another element or being shown as being located outside another element can be described as such reference. Additionally, a reference axis 399 is provided for describing the relative arrangement of parts. The reference axis 399 includes a z-axis as a vertical axis, wherein the z-axis increases from bottom to top (e.g., in the direction of the z-axis arrow). The topmost point has the maximum z-axis value, and is also the topmost point relative to gravity.

[0048] The liquid level sensor 230 includes a measuring tube 302 having a float 304 positioned therein. The measuring tube 302 is formed as an elongated hollow cylinder (e.g., extending in the vertical direction) having an inner diameter and an outer diameter, and the outer diameter and the inner diameter are separated by the wall thickness of the measuring tube. The float 304 is formed as a sphere having an outer diameter smaller than the inner diameter of the measuring tube 302. Because the outer diameter of the float 304 is smaller than the inner diameter of the measuring tube 302, the float 304 can move freely between the upper boundary and the lower boundary along the length of the measuring tube 302 (e.g., in the vertical z direction), as will be described in detail below. In addition, the difference between the outer diameter of the float 304 and the inner diameter of the measuring tube 302 can be very small, so that the float 304 will not be significantly translated in the (horizontal) x-direction and y-direction within the measuring tube 302.

[0049] Measuring tube 302 and float 304 can each be made of (for example, non-reactive) materials compatible with one or more anesthetic agents. In addition, measuring tube 302, in particular the inner surface of measuring tube 302, can be made of smooth anti-reflective material. In an exemplary embodiment, measuring tube 302 is made of aluminum and includes black nickel plating on the inner surface. In another exemplary embodiment, measuring tube 302 is made of black extruded polypropylene. In another embodiment, measuring tube 302 is made of opaque high-density polyethylene. Float 304 can be made of reflective material, the density of which is less than the density of the anesthetic agent to be measured using liquid level sensor 230, so that float 304 can be located on or at the surface of the liquid anesthetic agent. As an exemplary embodiment, float 304 can be made of white nylon. As another exemplary embodiment, float 304 can be made of white polypropylene. Further, in some embodiments, a reflector and / or a focusing lens can be positioned on float 304, such as attached to the topmost surface of float 304.

[0050] The level sensor 230 also includes a cover 306 that is coupled to a bottom portion (relative to the page and relative to gravity) of the measuring tube 302. Figure 3 In the illustrated embodiment, the cover 306 is interlocked with the bottommost surface of the measuring tube 302, such as by fitting the lip of the cover 306 into the groove on the measuring tube 302. In addition, the cover 306 includes a circular central opening whose inner diameter is less than the outer diameter of the float 304. When the measuring tube is positioned in the storage tank, as will be elaborated in detail below, the circular central opening can fluidically connect the interior of the measuring tube 302 to the interior of the storage tank. That is, the liquid anesthetic stored in the storage tank can enter and leave the bottom of the measuring tube 302 via the central opening of the cover 306, so that the liquid anesthetic can flow between the interior of the measuring tube 302 and the rest of the storage tank (e.g., the outside of the measuring tube 302). In addition, the central opening of the cover 306 forms a contraction that prevents the float 304 from leaving the measuring tube 302. Therefore, the float 304 can be located on or at the surface of the liquid anesthetic in the measuring tube 302, and the central opening of the cover 306 can define the lower boundary of the vertical movement of the float 304.

[0051] The measuring tube 302 may also include one or more vents 308 at or near the top of the measuring tube. The vents 308 may allow gas to transfer (thus achieving pressure equalization) between the interior of the measuring tube 302 and the exterior of the measuring tube 302 (e.g., the interior of the storage tank), thereby preventing pressure buildup or vacuum formation in the interior of the measuring tube 302. For example, as will be described in Figure 8As shown in FIG. 1 , the vertical position of the float 304 changes as the liquid level of the liquid anesthetic agent changes. As the liquid level (e.g., height) increases, the vertical position of the float 304 increases (e.g., relative to the z-axis), thereby forcing the gas molecules to leave the measuring tube 302 from above the float 304 and pass through the vent 308 to reach the outside of the measuring tube 302. That is, the volume above the float 304 decreases as the float 304 rises in the measuring tube 302, so that the gas flows out of the inside of the measuring tube 302 via the vent 308 to prevent the pressure above the float 304 from increasing (such an increase in pressure may hinder the vertical movement of the float 304). As the liquid level decreases, the vertical position of the float 304 decreases, thereby sucking in gas molecules from the outside of the measuring tube 302 via the vent 308. That is, the volume above the float 304 increases and the float 304 descends within the measuring tube 302, so that gas flows into the interior of the measuring tube 302 via the vent 308 to prevent a vacuum from forming above the float 304 and to maintain a relatively constant pressure above the float 304. In summary, pressure equalization helps ensure that when the measuring tube 302 is at least partially submerged in the liquid anesthetic agent, the level (e.g., height) of the liquid anesthetic agent within the measuring tube 302 is substantially equal to the level of the liquid anesthetic agent outside of the measuring tube 302 within the reservoir.

[0052] The level sensor 230 also includes a retaining bracket 310 coupled to the top portion of the measuring tube 302 (such as positioned on the topmost surface of the measuring tube 302). As shown, the retaining bracket 310 may include forks extending into the interior of the measuring tube 302, each fork having a lip shaped to engage with a corresponding opening in the measuring tube 302. The engagement of the forks of the retaining bracket 310 with the measuring tube 302 secures (e.g., removably couples) the retaining bracket 310 to the measuring tube 302. The distance between the forks across the measuring tube 302 is less than the outer diameter of the float 304, and therefore, the forks of the retaining bracket 310 form a constriction that limits the upper boundary of the vertical movement of the float 304 within the measuring tube 302.

[0053] Additionally, the retaining bracket 310 may couple the level sensor 230 to a sump (eg, Figure 2302) and can form an airtight seal with the tank via a seal 312 coupled within the retaining bracket 310. For example, the seal 312 can be an elastomeric seal, such as an O-ring, made of polytetrafluoroethylene (PTFE), neoprene, polyurethane, etc., which forms an airtight barrier between the tank and the retaining bracket 310. When the liquid level sensor 230 is coupled to the tank, the upper portion of the retaining bracket 310 (e.g., the portion of the retaining bracket 310 vertically located above the measuring tube 302) can be outside the tank, while the lower portion of the retaining bracket 310 (e.g., the portion of the retaining bracket 310 that is within the interior of the measuring tube 302) can be located within the interior of the tank. For example, the top wall of the housing of the tank may include an opening that is shaped to receive the measuring tube 302 so that the measuring tube 302 extends into the interior of the tank. The opening in the tank housing can have an inner diameter that is larger than the outer diameter of the measuring tube 302 so that the measuring tube 302 can be lowered vertically therein, but is small enough so that horizontal movement of the measuring tube 302 is limited. In addition, the opening in the tank housing can be smaller than the width of the upper portion of the holding bracket 310.

[0054] The retaining bracket 310 additionally houses an optical window 318 and an optical sensor 320, which can be connected to a controller (e.g., Figure 2 In one embodiment, the optical sensor 320 is a proximity sensor including at least one light emitter and at least one light detector, as will be described below with respect to Figure 4 In other embodiments, the optical sensor 320 may be another type of optical sensor that can be used to determine the distance to a measurement target, such as a structured light sensor or a laser Doppler vibrometer.

[0055] The optical sensor 320 is positioned to emit light toward the interior of the measuring tube 302 (e.g., via at least one light emitter) in a top-down manner, and to receive light from the interior of the measuring tube 302 (e.g., via at least one light emitter). The optical window 318 is shown as being positioned vertically below the optical sensor 320, between the optical sensor 320 and the interior of the measuring tube 302, and can be formed of a transparent polymer (e.g., polyphenylsulfone), a crystalline material (e.g., sapphire glass), or another suitable material that has high optical transmittance in the emission range of the light source and has high anesthetic compatibility. In some embodiments, the optical window 318 can also be used as a focusing lens. Although in Figure 3 In the example embodiment, the optical window 318 is shown as a flat window, but it is understood that the optical window 318 can have various geometric shapes or be configured as various lens types, such as a hemispherical lens, a spherical lens, or a Fresnel lens.

[0056] Continue to see Figure 4 , showing Figure 3 Surface view of the optical sensor 320 introduced in FIG. Specifically, Figure 4 An exemplary embodiment of a possible configuration of the optical sensor 320 is shown, but other configurations are possible and include Figure 3 The reference axis 399 introduced in FIG. Figure 3 and Figure 4 The relative orientation of the views shown in . For example, Figure 4 The view is in the xy plane, with the z axis going into the page. Figure 4 In the illustrated embodiment, the optical sensor 320 includes a light source 402, an ambient light detector 404, and a light detector 406 within a common housing 408. For example, the light source 402 may emit light through a first light emission aperture in the housing 408; the ambient light detector 404 may receive and detect light present outside the housing 408 via a second ambient light sensor aperture in the housing 408; and the light detector 406 may receive and detect light emitted by the light source 402 that has been reflected to the outside of the housing 408 via a third position return aperture in the housing 408. For example, the first aperture may form an illumination cone having a defined geometry for obtaining desired illumination characteristics, and the second aperture and the third aperture may form a field of view cone having a different defined geometry for obtaining desired light collection characteristics. However, in other embodiments, the ambient light detector 404 may not be included. Additionally, in some such embodiments, the light detector 406 may include a filter (such as a bandpass filter) to filter out ambient light that is not emitted by the light source 402.

[0057] The light source 402 can emit light of a defined wavelength or wavelength range when commanded (eg, powered on). Figure 3 The wire 322 shown receives the Figure 2 25. Command signal of controller 225 shown in the figure. For example, the command signal can include information about the intensity of the light to be emitted and the activation duty cycle. In some embodiments, light source 402 can emit light within the range of near infrared (NIR) or infrared (IR). For example, NIR and IR light of longer wavelengths can have less scattering (compared with visible light of shorter wavelengths), so that optical sensor 320 can detect longer distances. In some embodiments, light source 402 can emit light of a limited wavelength in the range between 800 nanometers (nm) and 950 nanometers (nm). As an exemplary embodiment, light source 402 can be configured to emit the light of 850nm. As another exemplary embodiment, light source 402 can be configured to emit the light of 940nm. For example, light source 402 can be a light emitting diode (LED) or a laser.

[0058] For example, ambient light detector 404 can be configured to detect light from a wide range of wavelengths across the visible spectrum, while light detector 406 can be configured to detect light from a narrow range of wavelengths that includes the wavelengths of light emitted by light source 402. Thus, at least in some embodiments, light detector 406 can be specifically configured to detect light emitted by light source 402. Additionally, due to the spacing between light source 402 and light detector 406 and the relatively narrow illumination cone of light source 402 and the relatively narrow field of view cone of light detector 406, light detector 406 may not be able to directly detect light emitted by light source 402. Instead, light detector 406 can detect light emitted by light source 402 that has been reflected, as will be discussed below with respect to FIG. Figure 5 As further described herein. For example, one or both of ambient light detector 404 and light detector 406 can be a variable wavelength detector or a diode array, and can each output a signal (e.g., in volts or amperes) based on a characteristic of the received light. For example, as the intensity of the received light increases, the voltage output of ambient light detector 404 or light detector 406 can increase. The signals output by ambient light detector 404 and light detector 406 can be received by a controller, which can perform various data processing actions, as further described herein.

[0059] Continue to see Figure 5 , schematic diagram 500 illustrates light emission and light detection by the optical sensor 320 of the liquid level sensor 230. Figures 2 to 4 Components introduced in are denoted by the same reference numerals and may not be reintroduced. Figure 5 Reference axis 399 is included to highlight the position of the component relative to Figure 3 and Figure 4 The relative arrangement of the views shown. For example, Figure 5 The view is in the xz plane with the y axis entering the page. In addition, a simplified view of the level sensor 230 is shown, and not all components are included, but it is understood that such components (e.g., measuring tube 302) may be present.

[0060] Schematic 500 shows a partial side view of a liquid level sensor 230 including an optical sensor 320 positioned directly above and in common surface contact with an optical window 318. The optical window 318 covers a light source 412, an ambient light detector 404, and a light detector 406, the locations of which are schematically illustrated by dashed lines. The float 304 is partially shown at a distance below the optical window 318 (and not in direct contact with it).

[0061] In general, the optical sensor 320 can be used to determine the travel time of a photon of light from an emitter (e.g., light source 402) to a detector (e.g., ambient light detector 404 or light detector 406), which is positively correlated to the distance traveled by the photon of light. As will be elaborated below, the light emitted by the light source 402 can be at least partially reflected by a target (e.g., float 304) and directed back to the optical sensor 320. The time delay between the emission of light by the light source 402 and the detection of light by the light detector 406 can be determined as the travel time of the photon of light. Because the speed of light is a known constant, the travel time multiplied by the speed of light is equivalent to the distance that the photon of light has traveled. As a non-limiting illustrative example, a 1 cm distance between the optical sensor 320 and the reflector can result in a travel time of 66 picoseconds. In addition, the travel time is not affected by the reflectivity of the target, but a high reflectivity can increase the amount (or intensity) of light reflected.

[0062] Light emitted by light source 402 is directed downward toward optical window 318. Because optical window 318 is transparent, at least a portion of the light emitted by light source 402 passes through optical window 318, while a portion may be reflected by the optical window (e.g., at a window / gas interface). Light source 402 may be activated to emit light in pulses, each pulse having a predetermined duration and with a predetermined interval between each pulse. For example, controller 225 ( Figure 5 4. (not shown) can command the light source 402 at a predetermined activation duty cycle according to instructions stored in the memory. As an illustrative example, the schematic diagram 500 shows the optical paths of three different light photons emitted by the light source 402, including the optical path 502, the optical path 504 and the optical path 506.

[0063] Light in optical path 502 is reflected by optical window 318 and received by ambient light detector 404, which may also receive any ambient light present. Figure 5 ) and its storage tank 222 ( Figure 5406). The position of the ambient light detector 404 within the optical window 318 (also not shown) can reduce ambient light exposure, but the ambient light detector 404 can compensate for optical crosstalk and high ambient light conditions and light distortion caused by the optical window 318. For example, the controller can receive a signal output from the ambient light detector 404, which can correspond to the intensity of all light (including light in the optical path 502 in addition to any ambient light), and use the signal output from the ambient light detector 404 to adjust the distance calculation using the measurement received from the light detector 406 according to the instructions stored in the memory. As an example, because the light source 402 can emit light in pulses and the ambient light can remain relatively constant, the controller can determine the intensity of the ambient light present based on the relatively constant signal component received from the ambient light sensor 404. In addition, the controller can subtract the determined ambient light intensity from the signal output by the light detector 406. In another embodiment, the optically opaque feature can be disposed within the optical window and between the light source 402 and the light detector 406, thereby forming separate windows (e.g., one window for the emitter and one window for the detector) to prevent and / or reduce optical crosstalk.

[0064] Light in the optical path 504 is reflected by the optical window 318 (e.g., at the window / gas interface) and received by the light detector 406. However, because the optical window 318 is a fixed, known distance from the light detector 406, the controller can identify the signal output by the light detector 406 that corresponds to the reflection occurring by the optical window 318. In contrast, the distance of the float 304 from the light source 402 and the light detector 406 is variable. Light in the optical path 506 is reflected by the float 304 and received by the light detector 406. The elapsed time between the light source 402 emitting light and the light detector 406 receiving light reflected by the float 304 (e.g., in the optical path 506) varies based on the distance between the float 304 and the optical sensor 320. For example, as the distance between the float 304 and the optical sensor 320 increases, the elapsed time increases, and as the distance between the float 304 and the optical sensor 320 decreases, the elapsed time decreases. The controller can receive the signal output by the light detector 406 (e.g., via Figure 3322 as shown), which directly corresponds to the distance between the float 304 (and therefore the surface of the liquid anesthetic agent in the measuring tube) and the optical sensor 320. For example, the controller may include a lookup table, graph, or function stored in memory that relates the signal output by the light detector 406 to the distance between the float 304 and the optical sensor 320, and takes into account sensor calibration (to account for distortion caused by the optical window 318, the height of the float 304 above the liquid level, etc.). In an alternative embodiment, the signal output by the light detector 406 may correspond to the elapsed time, and the controller may calculate the distance to the surface of the liquid anesthetic agent in the measuring tube 302 based on the elapsed time and the speed of light according to instructions stored in memory as described above, which instructions may also take into account sensor calibration.

[0065] Figure 6 shows the level sensor (e.g., relative to Figures 2 to 5 600 is an example graph of the relationship between the number of measurement samples measured by the liquid level sensor 230 and the distance of the liquid surface from the liquid level sensor. The number of measurement samples is shown on the horizontal axis, and the number of measurement samples increases from left to right and increases with time. For example, each measurement sample can refer to a discrete measurement made by the liquid level sensor, such as a light pulse emitted by the light source 402 and a corresponding detection by the light detector 406, each of which is Figure 4 The vertical axis shows the distance of the liquid surface from the liquid level sensor, where the liquid surface distance increases from bottom to top along the vertical axis. In the example of graph 600, the liquid surface is an anesthetic gasifier (such as according to Figure 2 The surface of the liquid anesthetic agent in the storage tank of the system shown.

[0066] Graph 600 includes a graph 602 showing how the distance of the liquid surface from the sensor changes as the tank is drained during a continuous measurement period from a minimum number of measured samples to a maximum number of measured samples. Graph 600 also includes a first boundary 604 and a second boundary 606, wherein the first boundary corresponds to a minimum liquid surface distance from the sensor that the sensor can measure and the second boundary corresponds to a maximum surface distance from the sensor that the sensor can measure. For example, the first boundary 604 and the second boundary 606 can be defined by physical constraints of the liquid level sensor, such as those described above with respect to Figure 3 The constriction defines a boundary of vertical movement of the measurement target (eg, float 304 ) within the measurement tube (eg, measurement tube 302 ).

[0067] The sump is completely full at the beginning of the measurement cycle (e.g., the first measurement sample). Therefore, the float is at the closest position it can reach to the level sensor, and thus the liquid surface distance from the sensor (graph 602) measured by the level sensor is equal to the first boundary 604. As the sump is emptied during the measurement cycle, the measured liquid surface distance from the sensor (graph 602) increases, corresponding to a decrease in the level (and volume) of the liquid anesthetic agent in the sump. The measured liquid surface distance from the sensor (graph 602) approaches the second boundary 606 near the end of the measurement cycle, and reaches the second boundary 606 at the last measurement sample. For example, the float is at the farthest position it can reach from the level sensor, and therefore, even if the liquid level continues to decrease, the level sensor may not detect these changes.

[0068] In addition, the controller (e.g. Figure 2 The controller 225) can use the measured distance of the liquid surface from the sensor to determine the volume of liquid in the tank based on a pre-calibrated relationship stored in memory. Figure 7 , example graph 700 shows a graph 702 of an inverse linear relationship between a measured distance of a liquid surface from a sensor and a volume of liquid in a sump. Graph 700 includes as a horizontal axis the measured distance of the liquid surface from the sensor, where the distance increases from left to right along the horizontal axis, and as a vertical axis the volume of liquid in the sump, where the volume of liquid increases from bottom to top along the vertical axis.

[0069] Graph 702 shows that as the measured distance from the liquid surface of the sensor increases, the volume of the liquid anesthetic in the reservoir decreases. In addition, graph 702 is bounded by a lower boundary 704 and an upper boundary 706, where the lower boundary corresponds to the lowest volume that the sensor can measure and the upper boundary corresponds to the highest volume that the sensor can measure. For example, lower boundary 704 may correspond to Figure 6 The second boundary 606 of represents the first lower volume of liquid anesthetic agent in the reservoir when the float reaches its lowest possible position in the measuring tube. The upper boundary 706 may correspond to Figure 6 The first boundary 604 of represents the second higher volume of liquid anesthetic agent in the storage tank when the float reaches its highest possible position in the measuring tube. Both the lower boundary 704 and the upper boundary 706 can be pre-calibrated values, which can be changed based on the size (e.g., capacity) and geometry of the storage tank.

[0070] In one embodiment, the controller can determine the volume of liquid in the sump with reference to graph 700, such as by using graph 702 to determine the corresponding volume of liquid for the received measured distance from the liquid surface of the sensor. In another embodiment, the controller can additionally or alternatively refer to a lookup table defining the values ​​of graph 702. For example, the controller can input the measured distance from the liquid surface of the sensor into a lookup table, which can output the corresponding volume of liquid in the sump. In yet another embodiment, the controller can additionally or alternatively determine the volume of liquid in the sump based on the measured distance from the surface of the sensor. For example, the controller can input the measured distance from the liquid surface of the sensor into a formula defining the relationship shown in graph 702, which can output the corresponding volume of liquid in the sump.

[0071] Next, Figure 8 An example timeline 800 is schematically shown that illustrates the use of an optical ToF proximity sensor for determining the anesthetic agent level in an anesthetic agent vaporizer. The anesthetic agent vaporizer may be Figure 2 The anesthetic agent vaporizer 200 described in the embodiment of the present invention includes a liquid level sensor 230 connected to the storage tank 222. Figure 8 in and previously in Figure 2 and Figure 3 Components with the same functions as those described in the previous section are denoted by the same reference numerals and may not be reintroduced. In addition, for simplicity, some components of the anesthetic vaporizer 200 and the liquid level sensor 230 are not shown in this example of the timeline 800, but it is understood that such components exist. The controller 225 ( Figure 8 222) may perform one or more methods to determine the volume of liquid anesthetic agent 210 within tank 222 based on data received from level sensor 230, such as described below with respect to Fig. 9 The example method described.

[0072] The timeline 800 shows a plurality of “snapshots”, each representing an instantaneous depiction of the amount (e.g., volume) of the liquid anesthetic agent 210 within the reservoir 222 at a corresponding time, including a first snapshot 802 at a first time t1, a second snapshot 804 at a second time t2, a third snapshot 806 at a third time t3, and a fourth snapshot 808 at a fourth time t4. The first time is the earliest time, and the fourth time is the latest time, as indicated by the direction of the timeline 801. In particular, each snapshot shows how the float 304 moves vertically as the level of the liquid anesthetic agent 210 within the reservoir 222 (and therefore within the measuring tube 302) changes, and the resulting change in the distance to the float 304 measured by the optical sensor 320.

[0073] The first snapshot 802 shows the float 304 at a first distance d1 from the optical sensor 320. Additionally, the float 304 is between a minimum level 810 (e.g., corresponding to the maximum possible distance between the optical sensor 320 and the float 304, such as corresponding to Figure 6 The second boundary 606 of the embodiment of the present invention) and the maximum liquid level 812 (eg, corresponding to the minimum possible distance between the optical sensor 320 and the float 304, such as corresponding to Figure 6 For example, the topmost surface of the float 304 cannot drop below the minimum liquid level 810 due to the restriction at the bottom of the measuring tube 302. Similarly, the topmost surface of the float 304 cannot rise above the maximum liquid level 812 due to the restriction near the top of the measuring tube 302, thereby creating a "dead space" at the top of the tube. Therefore, only liquid levels between the minimum liquid level 810 and the maximum liquid level 812 (e.g., above the minimum liquid level 810 and below the maximum liquid level 812) result in accurate liquid level measurements by the optical sensor 320. Because the first distance d1 is between the minimum liquid level 810 and the maximum liquid level 612, the controller calculates the correct liquid level based on the first distance measurement received from the optical sensor 320, such as by inputting d1 into one or more pre-calibrated lookup tables, formulas, or graphs (such as those described above with respect to Figure 7 In the graph 700), the volume of the liquid anesthetic agent 210 is accurately calculated as the first volume V1.

[0074] Between time t1 and time t2, the anesthetic agent vaporizer is operated to deliver anesthetic agent to the patient. As shown in the second snapshot 804, the vertical height of the float 304 decreases as the vertical height of the liquid anesthetic agent 210 in and outside the measuring tube 302 decreases. The float 304 is a second distance d2 away from the optical sensor 320, which is greater than the first distance d1 at time t1. The second distance d2 remains between the minimum liquid level 810 and the maximum liquid level 612, so the controller accurately calculates the volume of the liquid anesthetic agent 210 as a second volume V2 based on the second distance measurement received from the optical sensor 320, which is less than V1.

[0075] The anesthetic agent vaporizer continues to operate between time t2 and time t3. The third snapshot 806 shows that the float 304 is a third distance d3 from the optical sensor 320, which is greater than each of the first distance d1 and the second distance d2. In addition, the liquid level of the liquid anesthetic agent 210 in the storage tank 222 has dropped below the minimum liquid level 810, and the measuring tube 302 is no longer at least partially immersed in the liquid anesthetic agent 210. Therefore, the controller cannot accurately calculate the third volume V3 based on the third distance measurement received from the optical sensor 320, but can recognize that the float 304 has reached the minimum liquid level 810 based on the measured third distance d3. In some embodiments, the controller can take action in response to measuring the third distance d3, such as outputting an alarm to refill the storage tank.

[0076] The storage tank 222 is refilled between time t3 and time t4. As shown in the fourth snapshot 808, the vertical height of the float 304 increases due to the refilled liquid anesthetic agent 210. The float 304 is a fourth distance d4 away from the optical sensor 320, which is the minimum distance shown in the timeline 800, and remains between the minimum liquid level 810 and the maximum liquid level 612. The controller accurately calculates the volume of the liquid anesthetic agent 210 as a fourth volume V4 based on the fourth distance measurement received from the optical sensor 320, which is the maximum volume shown in the timeline 800. In some embodiments, the controller can communicate with the controller via a human-machine interface (e.g., Figure 2 The controller may provide real-time fill information on a display of an HMI 226 to indicate the fill level based on a signal received from the optical sensor 230 during refilling. This feature may be used to prevent unexpected potential overfilling / overflow of liquid anesthetic agent by providing an alarm to a user and / or closing a valve that fluidly couples the inlet fill port to the reservoir. For example, the controller may output the real-time volume (or level) of the liquid anesthetic agent 210 determined by the level sensor 230 via the HMI, and may further output an overfill alarm and / or actuate the inlet fill port valve closure in response to the volume (or level) exceeding a maximum volume (or level).

[0077] Now turn to Fig. 9 , shows a high-level flow chart of an example method 900 for determining the volume of liquid anesthetic agent in an anesthetic agent vaporizer tank using a liquid level sensor. The method 900 may be executed by a controller such as Figure 2 Controller 225) according to the memory stored in the controller (for example, Figure 2 228) and in combination with one or more inputs (such as via a human-machine interface (e.g., Figure 2 The HMI 226 receives input from an operator) and one or more sensors (e.g., Figure 2In addition, the controller can output information to the operator of the anesthesia machine via a human-machine interface. Although method 900 will be relative to Figure 2 The anesthetic agent vaporizer 200 is described with reference to the figure, but it will be appreciated that the method 900 may be applied to any anesthetic agent vaporizer configuration including an electronic controller and a level sensor using time-of-flight sensing.

[0078] At 902, the distance to the measurement target is measured via an optical sensor. The optical sensor is a proximity sensing component of a liquid level sensor (e.g., Figure 3 ), and the measurement target may be positioned in a non-reflective measuring tube (e.g., Figure 3 The reflective float (e.g., Figure 3 Measuring the distance to the measurement target via the optical sensor may include operating a light source of the optical sensor (e.g., Figures 4 to 5 ) to emit pulses of light at a predetermined operating duty cycle, and to measure the emission of each pulse with a light detector (e.g., Figures 4 to 5 The time elapsed between light detections by the light detector 406 shown in FIG. Figure 5 To elaborate, the optical sensor may output a signal corresponding to the distance and / or corresponding to the elapsed time to the controller.

[0079] At 904, the volume of anesthetic agent in the tank is determined based on the measured distance. The controller may store a pre-calibrated relationship between the measured distance and the volume of anesthetic agent in a memory, such as as a graph, a lookup table, or a formula. Thus, the controller may input the measured distance into a graph, a lookup table, or a formula, which may output a corresponding volume of anesthetic agent that produces the measured distance. As described above with respect to Figure 7 As mentioned, the pre-calibrated relationship can be specific to each tank configuration (e.g., volume capacity and / or geometry). As an example, for the same volume capacity, when the tank is narrower and taller, a smaller volume change can result in a larger distance change between the optical sensor and the measurement target than when the tank is wider and shorter.

[0080] At 906, the fresh gas flow rate and output anesthetic agent concentration are received. For example, the controller may receive a fresh gas flow rate and output anesthetic agent concentration from a concentration sensor (e.g., Figure 2The controller may include a concentration sensor 256 (e.g., a first mass flow sensor 241) that measures the anesthetic concentration output by the anesthetic vaporizer, and a fresh gas flow rate measurement from a mass flow sensor (e.g., a first mass flow sensor 241) that indicates the flow rate of fresh gas entering the anesthetic vaporizer. Alternatively, the controller may receive an output anesthetic concentration set value and a fresh gas flow rate set value from an operator via a human-machine interface. For example, the controller may use the set values ​​when the measured values ​​are not available.

[0081] At 908, an emptying time is calculated based on the determined anesthetic volume (e.g., as determined at 904), the fresh gas flow rate, and the output anesthetic concentration. The emptying time refers to the remaining duration until the volume of the liquid anesthetic in the storage tank is exhausted. Additionally or alternatively, the emptying time refers to the remaining operating time of the anesthetic vaporizer using the current operating conditions. In one embodiment, the emptying time may correspond to the remaining duration until the volume of the liquid anesthetic reaches zero (e.g., the storage tank is completely empty). In another embodiment, the emptying time may correspond to the remaining duration until the volume of the liquid anesthetic reaches a non-zero volume (such as the lowest measurable volume obtained by a liquid level sensor).

[0082] In one embodiment, the controller may calculate the emptying time into one or more lookup tables, graphs, or formulas based on a moving average of the fresh gas flow rate (e.g., over a predetermined duration of anesthetic agent use, such as a duration in the range of 1 to 5 minutes), a moving average of the output anesthetic agent concentration (e.g., over the duration), and a determined volume of anesthetic agent in the sump. As an example, the controller may calculate the emptying time using the following formula:

[0083]

[0084]

[0085] Formula 1 yields the term "Saturated_Gas_Volume" in milliliters (mL), which corresponds to the amount of vaporized anesthetic produced at a given temperature (T) of the anesthetic for the type of anesthetic used. The term "SW" is the specific gravity of the anesthetic in g / mL, which is selected based on the type of anesthetic used (e.g., 1.49 g / mL for isoflurane, 1.53 g / mL for sevoflurane, or 1.47 g / mL for desflurane). For example, the controller can input the type of anesthetic into a lookup table, which can output the specific gravity of the given type of anesthetic. The term "GC" is the Avogadro gas constant, which is a universal constant for all gases (e.g., regardless of the type of anesthetic used) and defines that under standard temperature and pressure conditions, 1 mole of any gas, dry (e.g., STPD, corresponding to a temperature of 273K and 1 atmosphere of pressure, without water vapor) contains 6.022×10 23 molecules, which occupy a volume of 22,400 mL. The term "MW" is the molecular weight of the anesthetic used in g / mol, which is selected based on the type of anesthetic used (e.g., 184 g / mol for isoflurane, 200 g / mol for sevoflurane, or 168 g / mol for desflurane). For example, the controller can input the type of anesthetic into a separate lookup table, which can output the molecular weight of a given type of anesthetic.

[0086] The Saturated_Gas_Volume calculated via Equation 1 may be used in Equation 2 to determine Time_to_Empty (in minutes), which corresponds to the duration remaining before the sump is emptied at the current anesthetic agent usage rate. In Equation 2, the term "Ave_FGF" is the average fresh gas flow rate (in mL / min), the term "Ave_Agent_Conc" is the average output anesthetic agent concentration (in % volume), and the term "Volume_in_Sump" is the anesthetic agent volume determined via the optical sensor (e.g., at 904).

[0087] At 910, it is determined whether the drain time is less than a threshold duration. The threshold duration may be a non-zero duration corresponding to the remaining time of anesthetic use, below which a refill of the reservoir is indicated. For example, the threshold duration may provide a time buffer to account for the expected amount of time that may be taken by an operator to refill the reservoir, thereby reducing instances where the reservoir becomes completely drained (or reaches a non-zero minimum volume).

[0088] If the emptying time is not less than the threshold duration, the method 900 proceeds to 912 and outputs the determined anesthetic volume and the calculated emptying time. For example, the controller can output the determined anesthetic volume (e.g., determined at 904) and the calculated emptying time (e.g., calculated at 908) via a human-machine interface (such as via one or more of a visual message and an audible message). The method 900 can then return so that the anesthetic volume and the emptying time can be updated when the optical sensor takes a new measurement.

[0089] If the emptying time is less than the threshold duration, the method 900 proceeds to 914 and outputs the determined anesthetic volume, the calculated emptying time, and the refill alarm. For example, in addition to outputting the determined anesthetic volume and the calculated emptying time, the controller may also transmit a refill alarm via the human-machine interface as described above at 912. In one embodiment, the refill alarm may include an audible alarm or message. In another embodiment, the refill alarm may additionally or alternatively include a visual message. The method 900 may then return.

[0090] Thus, the systems and methods described herein are used to determine and track the volume of anesthetic agent in an anesthetic vaporizer storage tank. As a result, a refill alarm can be output before the storage tank reaches an empty state. In addition, by determining the volume via an optical sensor using a top-down time-of-flight measurement, the measurement will not be affected by the characteristics of the anesthetic agent, which may change over time (due to the reactivity of the anesthetic agent, the temperature of the anesthetic agent, humidity, etc.). The technical effect of determining the volume of the liquid anesthetic agent via an optical time-of-flight sensor is that the accuracy of the determined volume can be increased.

[0091] As used herein, the elements or steps listed in the singular and beginning with the word "one" or "a kind of" should be understood as not excluding a plurality of the elements or steps, unless such exclusion is explicitly stated. In addition, the reference to "an embodiment" of the present invention is not intended to be interpreted as excluding the existence of additional embodiments that also include the cited features. In addition, unless explicitly stated to the contrary, the embodiment of "including", "comprising" or "having" an element or multiple elements with a specific characteristic may include additional such elements without the characteristic. The terms "including" and "in..." are used as the concise language equivalents of the corresponding terms "including" and "wherein". In addition, the terms "first", "second" and "third" etc. are only used as marks, and are not intended to impose numerical requirements or specific positional order on their objects.

[0092] This written description uses examples to disclose the invention, including the best mode, and also to enable a person of ordinary skill in the relevant art to practice the invention, including making and using any devices or systems and performing any included methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to a person of ordinary skill in the art. Such other examples are intended to fall within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with minor differences from the literal language of the claims.

Claims

1. A system for a liquid level sensor for an anesthetic vaporizer, include: a measuring tube including a float positioned therein, a bottom portion of the measuring tube being coupled to a cover having a central opening; a holding bracket coupled to a top portion surface of the measuring tube; an optical sensor housed within the holding bracket and comprising a light source positioned to emit light toward an interior of the measuring tube and a light detector positioned to receive light from the interior of the measuring tube; and an optical window received in the holding bracket and coupled between the optical sensor and the interior of the measuring tube, Wherein the retaining bracket includes a seal coupled therein, the seal forming an airtight barrier between the sump and the retaining bracket.

2. The system of claim 1, wherein the measuring tube is an elongated hollow cylinder composed of a non-reflective material, the float is a sphere composed of a reflective material, and the inner diameter of the central opening of the cover is smaller than the outer diameter of the float.

3. The system of claim 1 , wherein the retaining bracket is configured to couple the fluid level sensor to a tank of the anesthetic agent vaporizer, the retaining bracket is configured to be positioned on an exterior of the tank, and the measuring tube is configured to be positioned within the tank.

4. The system of claim 3, wherein the float has a lower density than the liquid anesthetic agent stored in the reservoir, and the vertical position of the float changes based on the height of the liquid anesthetic agent within the reservoir.

5. The system of claim 1, wherein the level sensor outputs a signal corresponding to a transit time of light emitted by the light source, reflected by the float, and received by the light detector.

6. The system of claim 1, wherein the float is constructed of at least one of nylon and polypropylene.

7. The system of claim 1, wherein the measuring tube is constructed of at least one of black nickel-plated aluminum and polypropylene.

8. The system of claim 1, wherein the optical window is comprised of at least one of polyphenylsulfone and sapphire glass.

9. A method for determining the emptying time of an anesthetic agent vaporizer using the system of any one of claims 1 to 8, include: Measuring the distance to the measurement target via an optical sensor; determining a volume of liquid anesthetic agent stored in a tank of the anesthetic agent vaporizer based on the measured distance; calculating the emptying time based in part on the determined volume; as well as An alarm is output in response to the calculated drain time being less than a threshold duration.

10. A system for an anesthetic agent vaporizer, include: a reservoir configured to hold a liquid anesthetic; a liquid level sensor comprising a retaining bracket coupled to a top exterior surface of the reservoir, a measuring tube extending from the retaining bracket into an interior of the reservoir and configured to be at least partially immersed in the liquid anesthetic agent, a float positioned within the measuring tube, and an optical sensor coupled within the retaining bracket vertically above the measuring tube, wherein the retaining bracket includes a seal that forms an airtight barrier between the reservoir and the retaining bracket; and A controller storing executable instructions in a non-transitory memory, the executable instructions, when executed, causing the controller to: operating the liquid level sensor to measure the distance between the optical sensor and the float; calculating a current volume of the liquid anesthetic agent in the tank and a remaining time until the tank is empty based on the distance measured by the level sensor; and A refill alarm is output in response to the remaining time decreasing below a threshold.

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